1. Field of the Invention
Embodiments of the present invention relate to a disk drive, and more particularly, to an actuator latch apparatus and a disk drive, with the same, locking an actuator in a predetermined position when a disk is not rotating, such that the actuator is prevented from arbitrarily rotating, e.g., due to an impact.
2. Description of the Related Art
A hard disk drive (HDD) is one of the data storage devices of a computer. The HDD reproduces data from a rotating disk and records data on the disk with a read/write head. In such an HDD, the read/write head reaches a desired position while moving above a recording surface of the rotating disk by way of an actuator and then executes the reproducing/recording functions.
Meanwhile, when the HDD is not operating, that is, when the disk is not rotating, the read/write head is parked off the recording surface of the disk in order to prevent a collision with the recording surface of the disk. Such head parking systems can be classified into a contact start-stop (CSS) system and a ramp loading system. In the CSS system, a parking zone in which data is non-recordable is provided along an inner circumference of the disk and the read/write head is parked in close contact with the parking zone. In the ramp loading system, the read/write head is parked on a ramp, which is installed along the outside the disk.
When the read/write head is parked on the parking zone or the ramp, the disk may randomly rotate, e.g., due to an impact or vibration, such that the read/write head is forced out of the parking zone or the ramp and onto the recording surface of the disk. In this case, the read/write head can make forceful contact with the recording surface of the disk, such that the read/write head and the recording surface may be damaged. Therefore, when the read/write head is parked on the parking zone or the ramp, the actuator should be locked in a predetermined position so that it cannot rotate arbitrarily. For this purpose, various kinds of actuator latch apparatuses have been provided in the HDD field.
FIG. 1 is a plane view schematically showing a HDD having a CSS head parking system according to the related art, FIG. 2 is a partial exploded perspective view of the HDD shown in FIG. 1, and FIG. 3 is a side view of a voice coil motor (VCM), illustrating an actuator latch apparatus according to the related art.
Referring to FIGS. 1 and 2, the HDD includes a disk 20 for recording data, a spindle motor 30 installed on a base member 10 to rotate the disk 20, and an actuator 40 provided with a read/write head 41. The read/write head 41 reads data from the disk 20 and writes data on the disk 20.
There are usually one or more stacked disks 20, with an evenly spaced relationship therebetween, and with the spindle motor 30 rotating the one or more disks 20. The disk 20 can be provided with a parking zone 21 along an inner circumference of data zone 22. When power is off, a slider 42 mounted with the read/write head 41 can be stably parked on the parking zone 21.
The actuator 40 is provided with a swing arm 46 that has a pivot hole 48, in a central portion thereof, such that the actuator 40 can be mounted rotatably about a pivot 47 installed on the base member 10. A suspension 44 is mounted on one end of the swing arm 46 to elastically bias the slider 42 toward a surface of the disk 20, in which the read/write head 41 is mounted on the slider 42.
A voice coil motor (VCM) 50 rotates the actuator 40. The VCM 50 includes a VCM coil 56 coupled to the other end portion of the swing arm 46, magnets 53 and 54 respectively positioned above and under the VCM coil 56, facing the VCM coil 56, a lower yoke 51 on which the magnet 53 is attached, and an upper yoke 52 on which the magnet 54 is attached. Screws 59 secure the lower and upper yokes 51 and 52 to the base member 10.
When the data recording and reproducing operations are executed, two forces, a lift force generated by the rotation of the disk 20 and an elastic force of the suspension 44, act on the slider 42, such that the slider 42 is lifted above the data zone 22 of the disk 20, with a height at which the lift and elastic forces are balanced, thereby allowing the read/write head 41 to read/write data from/to the rotating disk 20 while maintaining a predetermined distance therebetween.
Meanwhile, since the lift force lifting the slider 42 disappears when the HDD is powered down, such that the disk 20 is not rotating, the slider 42 must be taken from the data zone 22 before the lift force disappears, in order to prevent the data zone 22 from being damaged by coming into contact with the slider 42. In other words, if the VCM 50 rotates the swing arm 46 of the actuator 40 to move the slider 42 to the parking zone 21, before the rotation of the disk 20 stops, the slider 42 can be parked at the parking zone 21 when the disk 20 stops, thereby preventing damage of the data zone 21.
Referring to FIGS. 2 and 3, the HDD can be provided with an actuator latch apparatus that locks the actuator 40 to prevent rotation thereof after the slider 42 is parked on the parking zone 21 of the disk 20. That is, when the power is off, the actuator latch apparatus prevents the actuator 40 from arbitrarily rotating, e.g., due to an impact or vibration, such that the read/write head 41 can be prevented from escaping from the parking zone 21 and moving onto the data zone 22.
The actuator latch apparatus is a magnetic latch apparatus that uses the magnetic force of the magnet, 53 and 54. The actuator latch apparatus includes a metal piece 65 installed in an end of the swing arm 46 and an attracting part 66 formed in the upper yoke 52, for attracting the metal piece 65 with the magnetic force.
The installation structure of the metal piece 65 includes a protrusion 62 formed on the end of the swing arm 46, a damper insertion hole 63 formed through the protrusion 62 in a horizontal direction, a damper 64 securely inserted in the damper insertion hole 63, and the metal piece 65 attached on an end of the damper 64. The damper 64 decreases the amplitude of any impact generated when the metal piece 65 collides with the attracting part 66.
The attracting part 66 protrudes from an edge of the upper yoke 52 and is bent downward to meet a top surface of the lower yoke 51. A slot 67 can be formed in the attracting part 66, at a corresponding position to the metal piece 65, with a predetermined width. The magnets 53 and 54 can generate magnetic flux in the attraction part 66. Herein, a magnetic flux leakage takes place at the slot 67 and the magnetic flux leakage causes the metal piece 65 of the swing arm 46 to stick on the attracting part 66, thereby locking the actuator 40.
When the power is off, the metal piece 65 is caused to come into contact with the attracting part 66 by the magnetic force, such that the actuator 40 can be locked. Herein, a large latch force is suitable to prevent the attached metal piece 65 from being detached from the attracting part 66, e.g., due to an impact. Meanwhile, when the power is on, the actuator 40 also has to be unlocked to move the read/write head 41 to the data zone 22 of the disk 20. Herein, a small latch force would be suitable to easily detach the metal piece 65 from the attracting part 66.
However, if the actuator latch apparatus is designed to have the large latch force for a reliable locking of the actuator 40, a large torque has to be impulsively exerted on the actuator 40 in order to detach the metal piece 65 of the swing arm 46 from the attracting part 66, and therefore, available maximum current flows through the coil 56 coupled to the swing arm 46 to generate the large torque. However, because of the inertia force of the large torque, the swing arm 46 rotates fast enough that it collides with a stopper (not shown), even after the metal piece 65 of the swing arm 46 is detached from the attraction part 66, causing a “head slap” to occur. The head slap is a phenomenon in that the read/write head 41 of the actuator 40 collides with the surface of the disk 20, e.g., by an impact or vibration, such that the head slap can cause damage to the read/write head 41 or the surface of the disk 20. Therefore, to prevent the head slap, a brake needs to be applied to the swing arm 46 immediately after the detachment of the metal piece 65 and the attracting part 66. However, it is very difficult to control servo current, for applying the brake to the swing arm 46.
Thus, to provide a stable and reliable locking and unlocking operation of the actuator, there is required an improved actuator latch apparatus, in which a large latch force is applied when locking the actuator and only a small latch force needs to be applied when unlocking the actuator.